1. Field of the Invention
The present invention relates to the refinery industry and the removal of buildups of scale on the interior walls of refinery pipelines and furnaces produced by the refining of hydrocarbons. More particularly, the invention comprises a pipeline pig, a device with metallic scrapers for removing the built up scale from the interior walls of pipelines and furnace pipes.
2. Description of the Prior Art
In the petroleum refining process, lengths of furnace pipeline are heated in order to separate the various hydrocarbons into various petroleum products. In this separation process, the internal walls of furnace pipes become encrusted with baked on scale, restricting the flow rate and overheating the furnace pipelines. For years, steam xe2x80x9cdecokingxe2x80x9d has been the normal procedure for removing these scale buildups by blasting super heated steam through the pipelines to thermally crack the scale buildup, followed by washing with water to flush the loosened deposits from the pipeline. This steam decoking process, however, presents a number of potential problems, including potential damage to the pipeline from overheating or over pressurization, and releasing environmentally unsafe vapors when the steam is vented. Use of a pipeline pig would resolve many of these problems.
Over the past century, a number of different pipeline pigs have been developed for cleaning the interior of pipelines.
U.S. Pat. No. 646,545, issued to Franz Novotny on Apr. 3, 1900, relates to an apparatus for scouring and cleaning pipes or conduits, consisting of three distinct elements. The first element is a parabolic piston of a slightly smaller diameter than the pipe to be cleaned, which, when forced under pressure through the pipe pulls a second element of the device which is covered with scrapers for loosening any buildup. The scraper, in turn, pulls a wire brush which scours the pipe walls to further remove any buildup. The entire device is restrained against the pressure flow by a trailing guide line, with which it may be retrieved. The present invention is designed for the heat and pressure of refinery pipelines and provides additional flexibility in the pipeline pig""s composition to allow for sharper bends in the pipelines being cleaned.
U.S. Pat. No. 3,011,197, issued to Ulrich Nehse, et. al., on Dec. 5, 1961 and U.S. Pat. No. 5,343,323, issued to Harry J. Girard on Dec. 1, 1970, relate to pipeline cleaning devices constructed of polyurethane, wherein a harder outer surface covers a more resilient and flexible core. Nehse presents a generally spherical device while Girard a generally bullet shaped device. In both Nehse and Girard, scrubbing action is by friction between the polyurethane surface and the scale on the pipe. The present invention offers metallic scrapers for additional cutting action against buildups on pipe surfaces.
U.S. Pat. No. 3,651,530, issued to Ronald W. Schultz on Mar. 28, 1972 relates to a pipeline cleaning device constructed of a resiliently deformable material, generally spherical in shape, with a plurality of protuberances from its general surface providing scrubbing action. The protuberances are composed of the same material as the sphere, formulated to a greater hardness than the sphere. The present invention offers metallic scrapers for additional cutting action against buildup on pipe surfaces.
U.S. Pat. No. 3,863,287, issued to Kenneth M. Knapp, et. al., on Feb. 4, 1975, relates to a pipeline pig, generally bullet shaped, in which a polyurethane outer shell cast over an inner bladder of a resilient material, such that the outer shell can be replaced when worn down. Scrubbing action is provided by the edges of diamond shaped recesses in the surface of the outer shell. The present invention, again, offers metallic scrapers for additional cutting action against buildups.
U.S. Pat. No. 4,406,031, issued to Klaus Eimer, et. al., on Sep. 27, 1983 relates to a device for cleaning the interior of heat exchanger tubes. Eimer is composed of a sponge rubber ball with a plurality plastic bristles protruding from its surface for the cleaning of relatively small bore pipes. By contrast, the present invention is composed of a denser, more heat resistant rubber compound and provides metallic scrapers for additional cutting action against buildups.
U.S. Pat. No. 4,242,771, issued to Kenneth M. Knapp on Jan. 6, 1981; U.S. Pat. No. 4,244,073, issued to Sizuo Sagawa on Jan. 13, 1981; U.S. Pat. No. 5,150,493, issued to Edward L. Roberts on Sep. 29, 1992; and U.S. Pat. No. 5,924,158, issued to Robert C. Watts on Jul. 20, 1999, each refer to pipeline pigs generally cylindrical or bullet shaped, each with metallic studs protruding from a resilient body. The metallic studs provide increased cleaning ability over the polyurethane of the previously cited examples. Knapp, Sagawa, Roberts, Watts offer improvements over the cleaning ability of previous inventions, but, unlike the present invention, they fail to address the other major problem with pipeline pigs, that of becoming irretrievably stuck in a pipe. In order to avoid cutting the pipe to retrieve an irretrievable stuck pipeline pig, pipeline pigs composed entirely of polyurethane, or other polycarbonates, can often be melted by the application of external heat to the pipeline if they become stuck. By the introduction of metals into their composition, however, melting could tend to cause the studs to separate from the pipeline pig and fall into the pipeline. The present invention provides a preferable method of retrieval through its pressure release valves which allow the liquid/gel within the core of a stuck pipeline pig to escape, reducing the pressure the pipeline pig exerts against the internal surface of the pipeline.
None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed.
In the petroleum refining process, lengths of furnace pipeline are heated in order to separate the various hydrocarbons into various petroleum products. In this separation process, the internal walls of furnace pipes become encrusted with baked on scale, restricting the flow rate and overheating the furnace pipelines. For years, steam xe2x80x9cdecokingxe2x80x9d has been the normal procedure for removing these scale buildups by blasting super heated steam through the pipelines to thermally crack the scale buildup, followed by washing with water to flush the loosened deposits from the pipeline. This steam decoking process, however, presents a number of potential problems, including potential damage to the pipeline from overheating or over pressurization, and releasing environmentally unsafe vapors when the steam is vented. Use of a pipeline pig would resolve many of these problems, but existing pipeline pigs often present even more problems. Under heavy scaling conditions, the pipeline pig often gets stuck in the pipeline and pressure must be increased in an attempt to free the pipeline pig. This process often requires pressures in excess of manufacturer""s recommendations, occasionally causing blow outs of the pipeline, causing damage and/or personal injury. Alternatively, the pipeline must be cut to remove a stuck pipeline pig. Additionally, the placement of scrapers around the perimeter of many pipeline pigs is such that they do not cover the entire circumference of the pipe, leading to tracking in the scale, with each successive pipeline pig tending to follow the same tracks, eventually causing damage to the interior of the pipe.
Accordingly, it is a principal object of the invention to provide a pipeline pig which is economical to use.
It is another object of the invention to provide a pipeline pig which is easily removable if it becomes stuck in a pipeline.
It is a further object of the invention to provide a pipeline pig which provides effective cleaning of the full perimeter of the interior walls of a pipeline.
Still another object of the invention is to provide a pipeline pig which can be used in a variety of sizes of pipe.
An additional object of the invention is to provide a pipeline pig which can be used in a variety of types of pipes.
It is an object of the invention to provide improved elements and arrangements thereof in an apparatus for the purposes described which is inexpensive, dependable and fully effective in accomplishing its intended purposes.
Still another object of the invention is to provide a pipeline pig which can easily navigate sharper bends in pipelines.